Inductance coil



Jan. 13, 1931. A, GEBHARD INDUCTANCE COIL Filed March 9, 1929 2 Sheets-Sheet l MUH INVENTOR. 61 gefifa cb, Y

B #mpyw ATTORNEY Jan. 13, 1931. L. A. GEBHARD INDUCTANCE COIL Filed March 9, 1929 2 Sheets-Sheet 2 I N VEN TOR. M gm aw A TTOQNEY Patented Jan. 13,- 1931 UNITED STATES PATENT K OFFICE LOUIS A. GEBHARD, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB TO WIRED RADIO, rim, on NEW YORK, n. Y.,

A CORPORATION OF DELAWARE INDUcTANcE con.

' I Application'flled March 9,

My invention relates to inductance coils in general and more specifically to inductance coils of the type employed in high frequency transmitting systems.

An object of my invention is to provide an inductance coil wherein the temperature of of the coil is substantially independent of the current-in the coil and wherein the internal capacity is of a low value. H

Other and further objects of my invention reside in certain improvements in the design and structural features of inductance coils, a better understanding of which can be had. from the specification following and from the accompanying drawings, wherein:

Figure 1 represents a cross section of one turn of an inductance coil embodying my invention; Fig. 2 is a perspective view of the inductance coil of my-invention; 4 show sections of modified forms of my invention; Fig. 5 shows another modification of the inductance coil of my inventionyand Fig. 6 shows a section of -still another modi fication of the inductance coil of my invention.

In high frequency inductances the resistance is affected by skin effect upon the ,high frequency currents. For continuous current and low frequency alternating current, the current density is substantially uniform throughout the section of the conductor. If the conductor is large. in cross-section or the frequency is high,'the inner sections of the conductor carry a relatively small part of the total current, the densityof thecurre'nt being greatest at the surface of the conductor. The' distribution of current in a helical wound inductance is not uniform, however, throughout the surface of the conductor. The current is very high in the inside area of the conductor-and of a low order on the outer surface. When the turns of the inductance are close together this distribution will. modified Figs. 3 and 1929. Serial No. 345,740.

to a certain extent. With theturns close together, however, the capacity between the turns is increased. This increase in capacity is," in many instances, undesirable. The inductance coil of my invention is adapted to avoid the disadvantages of other types of coils, heretofore mentioned, a better understanding of which can be had from the specification following and by referring to the accompanying drawings.

F ig. 1 shows a cross section .of a turn of inductance embodying my invention. A flat metallic ribbon or strip. 1 represents the construction of the usual type of inductance coil .whichis wound in a helical form. as shown in Fig. 2. Metallic tubes brazed or welded to one side of strip 1, which 2 and'3 are soldered,

side is to be on the outside of the helical wound coil. Water or other liquid is admitted to tubes 2 and 3, the circulation of the liquid therethrough serving tocarry off any increase in'the temperature. In'Fig. 1 is shown a clip by means of which electrical connection with the turns of the inductance coil may be readily obtained. The clip con- I sists of a metallic strip 4j bent in the manner illustrated whereby the same fits around tubes 2 and 3. A screw .5 is threaded through-memher 4 and provided with a knurled head 6. Screw 5 may be replaced by a screw having a slotted head of small dimensions when the rough adjustments of the clip have been completed. Screw 5 is threaded in member 4 and provides means for associating an electric circuit therewith. In Fig. 2, the. ends 2a and 3a of tubular members 2 and'3 may be connected together; in this'manner the inflow of liquid would be in one of the members and the outfiow from the other. Rubber tubing may be employed for conducting the liquid to and away from tubular members 2 and 3. Members 2 and 3 maybe placed close together and the source of cooling fluid admitted to the two members at one end and conductedaway from the members at the other end of the inductance. Tubular members2 and 3 increase the capacitybetween the turns of the inductance.

only in proportion to the diameter of members 2 and 3 and this dimension, when com sidered that the tubular members are in the center of strip 1, adds only .a relatively small amount to thenormal' capacity of the strip.

The surface area'is greatly increased however and as the current density is normally greater on the'inner side of'the coil than onithe outer side, the circumference or-circular area serves adequately to carry the heat and the resistance does not rise to an excessive value. The

eddy currents created by the magnetic, field around the helix tend to produce undesirable heating but by continuously withdrawing such heat as generated the resistance of the coil remains substantially constant.

Fig. 3 shows a section of a modified form of the inductance coil'of my invention. In this modification metallic strip 1 corresponds to strip 1 shown in Figs. 1 and 2. Metallic tubular shaped member 8 is Welded, brazed or soldered to strip 1. Tubular shaped member Sisflattened and a part 9 is inserted through the tube in the center thereof, the walls of member 8 being pressed against part 9 whereby two individual passages 10 and 11 are obtained.

Figs. 4 and 5 show another modification of the inductance coil of my invention. In Fig. 4, a section is shown in detail, wherein a clamping connector similar to that shown in Fig. 1' is adapted to beassociated with an inductance of this design. A single tubular shaped member 12, of metal or an alloy there.-

of,'i's soldered, brazed or welded to metallic strip 1. Member 12 is partly flattened and has a depression 13 along the length thereof in such a manner as to provide two'passages 14 and 15 for the circulating liquid. The opposite walls of member 12 are deformed to provide the closed dividing portion 13.

Fig. 5 shows the inductance coil in its.

entirety with the clips removed therefrom. As explained .in connection with Fig. 2 the cooling fluid may beadmitted to tubular members 14 and 15 and carried from these members at the other ends 140 and 15a by rubber tubing. Without departing from my invention thecooling liquid may be admitted to member 14 or 15 where the ends 14a and 15a are interconnected and the outflow is from the same end of the inductance as the inflow. As in the arrangement shown in Fig. 2, the construction shown in Fig. 5-

serves adequatelymo carry off the excessive temperature which arises onthe inside of the -6 may be wound in a helicalform similar to the construction shown in Fig. 5.

I realize that many modifications of my invention other than those shown in the ac companying drawings and described in the foregoing specification are possible and it is tobeunderstood that my invention is. not limited by the foregoing specification or by the accompanying drawingbut only by the scope'of the-appended claims.

' What I claim as new'and desire to secure as follows: v v

1.- An inductance coil comprising in combination a helical wound metallic strip having associated therewith a'hollow metallic by Letters Patent of the United States is e fluid conducting member positioned on the side of said strip furthest from the axis of said coil.

2. An inductance coil comprising in com-.

bination a helical woundmetallic strip having associated therewith a plurality of hollow metallic fluid conducting members positioned on the outside of said strip.

3. An inductance coil comprising in com- I binationa metallic strip coiled in a helix having positioned on an electrically connected to the outermost side thereof a metallic tubular member running said metallic strip.

4; An inductancev coil comprising incomlengthwise with bination a helical formation of metallic strip wound flatwise with respect to the axis of said helix and a fluid conducting member 'of metallic material positioned upon the outside ofsaid strip.

5.-An inductance coil comprising in combination a length of metallic strip in the .form of a helix wherein the edges of said strip inone turn areadjacent to the edges 1n the other turns and metallic fluid conducting members positioned upon the out-- side of said strip and running parallel with the turns thereo 6. In an inductance coil wherein the current density is greatest in the portions of the conductor nearest the axis of said coil the combinationof metallic tubing associatedwith the portions furthest from the axis of said coil and'adapted to prevent a risein the temperature of said conductor without causing a substantial increase'inthe internal capacity ,of said'coil. I

7. An inductance coil comprising a; helical wound conductor and fluid. conducting memhers associated with the outside portions of said conductor for maintaining said helical wound conductor at substantially'constant temperature.

8. An inductance comprising a helically wound metallic conductor and a plurality of .fillld. conducting members. associated with said helically wound metallic conductor and I fluid conducting members being positioned with respect to said helically'wound conduc-' ist tor at the portions thereof where the current density is a minimum.- 4

9. In a helical wound hi h frequency inductance the combination of a tubular metallic member positioned on the outermost side of the conductor comprising said inductance.

10. In a. helical wound high frequency inductance the combination of a metallic tubular shaped member having the walls thereof depressed to form a plurality of individual fluid conducting paths positioned on and running parallel with the length of the electrical conductingmember constituting said inductance. I

LOUIS'A. GEBHARD. 

